Abstract
Purpose: Yin-hua Li-shi Decoction (YLD), a traditional Chinese medicine formulation, has been employed as a complementary therapy for atopic dermatitis (AD). Nevertheless, its precise therapeutic mechanisms remained unexplored. Methods: YLD components were identified by LC-MS, and quality control was performed using HPLC. In vitro, flow cytometry was used to assess YLD toxicity and its effect on inhibiting pro-inflammatory macrophages. In vivo, AD mice model was induced by daily topical MC903 application on mice ears for 15 days. Mice received oral YLD (1.50, 3.00, or 6.00 g/mL) once daily for 14 days. Disease progression was tracked by measuring skin thickness in mice. ELISA, western blot, and immunohistochemistry were used to analyze YLD ability to regulate inflammatory factors and restore skin barrier proteins. Flow cytometry was additionally used to investigate YLD modulatory effects on type I, II, and III adaptive immune responses. Results: YLD could inhibit the differentiation of macrophages into M1 phenotype in vitro. In the AD-like mice, YLD ameliorated epidermal hyperkeratosis and skin lesions, decreased the severity scoring of AD, and suppressed the inflammation of the skin in a dose-dependent manner. Moreover, YLD downregulated pro-inflammatory factors such as IL-4/13, TNF-α, TSLP, and IgE antibodies, restored the expression of barrier proteins in the skin, decreased the infiltration of CD4+ T cells in AD skin, and reestablished the balance of Th1/ Th2/ Th17 cells. Conclusion: YLD alleviated AD by regulating the adaptive immune response through modulation of T cell differentiation and cytokine production, and by restoring skin barrier function. The study revealed the therapeutic mechanism of YLD and provided experimental evidence supporting its application in AD treatment.